Increased seeding rates are closely associated with increased corn yields and allow hybrids to reach their full genetic potential. Average grower seeding rates have increased from 23,000 seeds/acre in 1985 to over 30,000 seeds/acre today. During that same time period, average yields have increased from about 105 to 160 bu/acre (Figure 1).
Figure 1. Average corn seeding rates reported by growers in the U.S. and Canada (DuPont Pioneer Brand Concentration Survey, 2013) and average U.S. corn yields (USDA/NASS).
Higher plant density causes increased competition between plants. When resources for moisture, light and nutrients are limited, interplant competition can lower yields. Through breeding, hybrids have been developed to be better suited for higher densities. For instance, hybrids now have more upright leaves to capture needed sunlight with less space, and root systems are more efficient with moisture uptake.
Every year DuPont Pioneer performs extensive plant population trials to determine optimum seeding rates, which can vary by hybrid and growing environment.
Research shows that hybrids with different maturities often have different population optimums. Early maturity hybrids usually require higher populations than later maturity hybrids (Figure 2).
Figure 2. Yield response to plant population from 4 maturity (CRM) ranges over 4 years.
Optimum populations also vary by yield; more productive soils can accommodate more plants and produce higher yields. DuPont Pioneer research trials indicate that optimum economic seeding rates can vary from about 27,000 seeds/acre for locations yielding less than 130 bu/acre, to about 38,300 seeds/acre for yields over 250 bu/acre. For the high yield levels common in many areas of the Midwest (190 – 220 bu/acre), the studies indicate an optimum economic seeding rate of 34,600 seeds/acre.
Figure 3. Corn yield response to population and optimum economic seeding rate by location yield level, 2006-2012.
Advances in variable-rate seeding (VRS) technology allow a greater degree of precision in selecting the optimum seeding rates for different hybrids and soils. To implement VRS, growers are encouraged to define crop management zones in a field by using long-term yield maps.
DuPont Pioneer offers growers an online planting rate estimator that provides recommendations based on a selected hybrid, grain price, seed cost and yield level. View the planting rate estimator on your desktop or from your Smartphone.